FFI и пользовательский тип данных

-- https://wiki.haskell.org/Foreign_Function_Interface#Data_structures
-- https://fresh2refresh.com/c-programming/c-structure-padding/
 
{-# LANGUAGE ForeignFunctionInterface #-}
 
import Foreign
import Foreign.C.Types
import System.Win32.Types (HANDLE, BOOL)
import Control.Applicative ((<$>), (<*>))
import Foreign.Storable
 
data COORD = COORD { x :: Int16
                               , y :: Int16 }
 
instance Storable COORD where
        alignment _ = 2
        sizeOf _    = 4
        peek ptr    = COORD
            <$> peekByteOff ptr 0
            <*> peekByteOff ptr 2
        poke ptr (COORD x y) = do
            pokeByteOff ptr 0 x
            pokeByteOff ptr 2 y
 
foreign import ccall "windows.h SetConsoleCursorPosition"

{-# LANGUAGE CPP,ForeignFunctionInterface #-}
 
#if defined(i386_HOST_ARCH)
#   define WINDOWS_CCONV stdcall
#elif defined(x86_64_HOST_ARCH)
#   define WINDOWS_CCONV ccall
#else
#   error Unknown mingw32 arch
#endif
 
import System.Win32.Types (HANDLE, BOOL, SHORT, DWORD)
import Graphics.Win32.Misc (getStdHandle,sTD_OUTPUT_HANDLE)
import qualified Control.Monad as CM (void)
import Data.Bits
 
newtype COORD = COORD DWORD
 
foreign import WINDOWS_CCONV "windows.h SetConsoleCursorPosition"
            setConsoleCursorPosition :: HANDLE -> COORD -> IO BOOL
 
mkCOORD:: SHORT -> SHORT -> COORD
mkCOORD x y = COORD $ ((fromIntegral y) `shiftL` 16) .|. (fromIntegral x)
 
main :: IO ()
main = do
    putStrLn "Hellow world"
    hOut <- getStdHandle  sTD_OUTPUT_HANDLE
    let cp = mkCOORD 5 3
    CM.void $ setConsoleCursorPosition hOut cp 
    CM.void $ getLine

getDlgItemInt :: HWND -> Int -> Bool -> IO Int
getDlgItemInt dlg item signed =
  alloca $ \ p_trans -> do
  res <- c_GetDlgItemInt dlg item p_trans signed
  failIfFalse_ "GetDlgItemInt" $ peek p_trans
  return (fromIntegral res)
foreign import WINDOWS_CCONV "windows.h GetDlgItemInt"
  c_GetDlgItemInt :: HWND -> Int -> Ptr Bool -> Bool -> IO UINT